List of river borders of U.S. states

Because of its unique history, many of the boundaries of the political divisions of the United States were artificially constructed (rather than permitted to evolve and drawn using natural features of the landscape). Therefore, many U.S. states have straight lines as boundaries, especially in the West. However, there are many partial state boundaries, particularly in the Midwest, Northeast, and South, that are defined by rivers; in fact, only four mainland states (Colorado, Montana, Utah, and Wyoming) completely lack any borders defined by rivers or waterways, as well as Hawaii whose borders are the islands.

Map of U.S. river/waterway state borders (highlighted)

The rule of the thread of the channel and its exceptions

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River boundaries are typically defined by the "thread of the channel" (the river's thalweg, usually in the approximate middle of the river's channel), under a rule that the United States inherited from England, where it applies to boundaries between counties.[citation needed] In the United States, there are at least six exceptions, however, where the boundary is one bank of the river rather than the thread of the channel:

List of river borders

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The course of the Charles River was used to indirectly define the border between Massachusetts and Rhode Island.[citation needed] The Merrimack River defines part of the border between Massachusetts and New Hampshire, which runs parallel to the river, three miles north of it (see Northern boundary of Massachusetts.)

List of US states with river borders

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Nearly every US states' border has some portion that is a river or other water way; 44 in total.

References

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  1. ^ Zimmerman, Joseph Francis (2007). Interstate Disputes: The Supreme Court's Original Jurisdiction. p. 74.
  2. ^ "Kentucky, Indiana and Ohio End River Boundary Dispute". The New York Times. Associated Press. October 21, 1981.
  3. ^ Campbell, Linda P.; Crimmins, Jerry (May 29, 1991). "High Court Gives Illinois a Piece of Ohio River". Chicago Tribune.